Clay Minerals, Paleochemistry and Diagenesis in Rift-Lake Environments

该项目将涉及详细的矿物学和化学 对大量长沉积岩芯中的粘土矿物进行了分析 到12米长），最近已收集到湖 东非的马拉维和图尔卡纳湖。 通过仔细分析 粘土组合的垂向变化及相关性 这些变化与硅藻含量，物理地层学和 淡水化学，我们将a）记录时间， 这些湖泊的古盐度波动程度 B）研究了这些变化的详细过程 碱性湖泊中的粘土矿物成岩作用，特别是 镁在蒙皂石相中的吸收和 蒙脱石转变为伊利石。 的 数据将与其他代用气候指标相关， 这些湖盆和以前的研究在东部其他地方 非洲帮助记录全球气候变化的模式 全新世。 此外，由于裂谷和碱性 湖泊是重要的沉积环境 在地质记录中， 在这些现代环境中的粘土矿物将有助于评估 埋藏成岩反应的作用， 石油在非海洋环境中的迁移。

This project will involve a detailed mineralogical and chemical analysis of the clay minerals in numerous long sediment-cores (up to 12m in length) which have been collected recently from Lake Malawi and Lake Turkana in East Africa. By analyzing carefully the vertical changes in the clay assemblages and correlating these with changes in diatom contents, physical stratigraphy and interstitial-water chemistry, we will a) document the timing and degree of paleosalinity fluctuations of these lakes during the last several thousand years and b) examine the detailed processes of clay-mineral diagenesis in alkaline lakes, especially the uptake of Mg in smectite phases and the transformation of smectite into illite under variable chemical conditions. The data will be correlated with other proxy climatic indicators from these lake basins and with previous studies elsewhere in East Africa to help document patterns of global climate change in the Holocene. Furthermore, since both rift-valleys and alkaline lakes are now recognized as important depositional environments in the geological record, an understanding of the behavior of clay minerals in these modern settings will help evaluate the role of burial diagenetic reactions for the generation and migration of petroleum in non-marine settings.